Also, HBO collects revenue from real subscribers based on the promise of high-quality content down the road. They satisfy this requirement often enough that a huge portion of all cable subscribers automatically upgrade to HBO. An a la carte model would allow those subscribers to wait-and-see; instead of investing effort to get engaged with a show like Treme, they'd sit back and wait for the show's merit to be validated by other people, and opt in only to the shows that were immediately compelling.